<?php
/**
 * Created by PhpStorm.
 * User: Administrator
 * Date: 2017/9/15
 * Time: 16:23
 */
var_dump($_SERVER);

$arr = array(
    'username'=>'frank',
    'age'=>19,
    'gener'=>true

);

$arr['city'] = 'hefei';
$arr['city'] = 'wuhu';
var_dump($arr);

unset($arr['city']);
var_dump($arr);